Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $107.61   6.382%   $114.4777   $114.48   $114.50   $114.50  
  Purchase #2 $183.30   5.422%   $193.2385   $193.24   $193.25   $193.20  
  Purchase #3 $23.88   13.294%   $27.0546   $27.05   $27.05   $27.10  
  Purchase #4 $237.41   9.345%   $259.596   $259.60   $259.60   $259.60  
  Purchase #5 $246.88   6.265%   $262.347   $262.35   $262.35   $262.30  
  Purchase #6 $150.25   8.573%   $163.1309   $163.13   $163.15   $163.10  
  Purchase #7 $58.86   4.709%   $61.6317   $61.63   $61.65   $61.60  
  7 purchase totals = $1,008.19       $1,081.4764   $1,081.48   $1,081.55   $1,081.40